Metal and method of producing the same



Dec. 29, 1936. C, SHERWQOD 2,065,618

METAL AND METHOD OF PRODUCING THE SAME Filed Dec. 28, 1933 2Sheets-Sheet l Dec. 29, 1936. c. F. sHERwooD 2,065,618

METAL AND METHOD OF PRODUCING THE SAME Filed Dec. 28, 193s zsheets-sheet 2 /35 I g Q2 5150' 32 30 I l l l l 35' 25 L Il 2.9 J 19 Q0g3 Patented Dec. 29, 1936 UNITE-D STATES PATENT OFFICE METAL AND METHODF PRODUCING THE SAME Delaware Application December Z8, 1933, Serial No.704,283

13 Claims.

This invention relates to an improved metal l and method of producingthe same.

The invention has especial reference to a metal for bearings and otherarticles having frictional surfaces, particularly engine pistons, valveguides, main bearings, and bearings of any form, and like articles, andis characterized by the formation of an oxide of iron packed into abriquetted shape and red to reduce the oxide to pure (or substantiallypure) iron and of an open porous structure.

It is to be understood, however, that the metal of the present inventionmay be employed in all similar or equivalent articles, or elsewhere assuitable and desired, and its characteristics may vary within the scopeof the appended claims.

The resulting product is a purer, more ductlle iron than can becommercially produced in any other way. It is of light weight and has alow coeiiicient of expansion. And it is of porous structure havingminute communicating pores distributed throughout the mass.

The oxide of iron packed into a briquetted shape and fired to reduce theoxide to pure (or substantially pure) iron, and of an Open porousstructure, particularly for bearings or other articles having frictionalsurfaces, is preferably impregnated with oil, and the metal soimpregnated sweats or exudes oil when heated and takes in or absorbs iton cooling.

The present invention further provides for utilizing at least twosources of raw material, particularly either copperas or millscale" forthe production of the present metal.

I prefer, however, making use of copperas, technically known as FeSO4.This is a Waste product usually obtained from pickling tanks or vats inthe pickling of iron, steel sheets, wire, bars and the like. 'I'hedisposal of this pickle liquid, after it becomes deficient in acid fromthe pickling operation, is a source of expense at the present time inthe manufacture of sheet metal products. In a plant in full operationthere are many tons per day of copperas which must be disposed of, incertain instances by hauling it from the plant in large wooden tanks onmotor trucks to articial ponds a distance away into which the liquor isdiscarded as a waste product and allowed to settle and evaporate bysolar evaporation. 'I'he cost of disposal of this pickle liquid isextremely high. There is, therefore, considerable economic advantage inmy utiliza tion of this material.

The present invention also provides for producing commercial sulphuricacid as a by-product of the present invention. This is a furthereconomic advantage of this particular aspect of the present invention.

It is to be understood, of course, that the present invention is not tobe, limited to production of the present metal from the particularsources of raw material referred to herein and that I intend to coverthe production of the present metal from all forms of iron oxide.

Further features and advantages will appear from the following detaileddescription taken in connection with the accompanying drawings, inwhich:

Figure l shows diagrammatically the several stages of the first step inthe process;

Figure 2 shows diagrammatlcally the second step in the process;

Figure 3 shows diagrammatically an alternative second step which may beemployed instead of the step shown in Figure 2;

Figure 4 shows diagrammatically the third step in the process;

Figure 5 shows diagrammatically the fourth step in the process;

Figure 6 shows diagrammatically the ilfth step in the process;

Figure 'I shows diagrammatically the sixth step in the process; and

Figure 8 shows diagrammatically the seventh and nal step.

I give the following examples of my process, but it will be understoodthat while in said examples I refer to certain sources of raw materialand to certain articles formed of the metal of the present invention,the oxide of iron which I employ may be obtained from other sources, andthe metal may be used in other articles. It will be understood furtherthat the analysis of the product will vary according to the raw materialused in its manufacture, and that the characteristics of the resultingproduct and the steps in the process may be varied considerably.

Where copperas or FeSO4, which is preferable, is used, the copperas isseparated from the supernatant liquid by evaporation or carefulcrystallization as shown at 5 in Figure 1. Ferrous sulphate crystals 6are thereby obtained having the formula FeSO4-|'7H2O. These crystals 6are then dehydrated in a kiln, or by any method known in the art ofmoisture evaporation, as indicated at 1 in Figure 1, producing ferroussulphate FeSO4 as indicated at 8.

'I'he ferrous sulphate is then calcined in a rotary kiln indicateddiagrammatically at 9 in Figure 2, which kiln is preferably capable ofbeing closed at both ends for purposes of driving off the sulphurcontent in the form of SO2 and S03. The temperature to which the kiln 9is subjected should not, so far as I am now aware, be over 1800 F., andpreferably should be between 1600 F. and 1800* F. This calcination inthe kiln 9 is carried on until no visible fumes of sulphur are apparent.After the sulphur content is driven off, with the ends of the kiln 9closed, city gas or, preferably, a reducing gas, such as can be made bythe cracking of methanes and butanes, is admitted to the kiln 9 at I0,and the Fe203, which has been produced by the elimination of the sulphurfrom the copperas, or FeSOi, is reduced by this gas to FeO, morecommonly known as black oxide, with a percentage of metallic iron.

It has been found that a percentage of 12% to 20% metallics can beobtained by using six cubic feet of gas per pound of FezOa in the kiln9.

'The time element depends upon the size of the kiln and the rabblingeffect obtained in the rotary action of the kiln. In producing 200pounds of product, the time element for calcination or eliminating thesulphur would be approximately two and one-half hours. The time forreduction under gas from FezOa to FeO would be from forty-five to sixtyminutes. The size of the kiln used in on' commercial adaptation of theinvention is thirty inches in diameter and fifty-four inches long, redfrom the exterior, and rotating at 12 R. P. M., but this, of course, maybe varied considerably.

The calcination of ores is common metallurgical practice, especially inzinc industries where sphalerite or zinc sulphide is calcined to zincoxide. Kilns, known as Mathison and Hegler, Merton, Hereschoif, andWedge, are used for this purpose. I make reference to these kilns asbeing suitable for this step of the present process.

I propose, in conjunction with the production of FeO containingmetallics, that is, FeC-I-Fe, to make use of the SO2 and S03 which isproduced during calcination and driven off at I2 in Figure 2 for theproduction of sulphuric acid. 'I'his can be done in the Well knownchamber process or contact process, making use of a catalytic agent.These fumes being very dense and concentrated as they come from the kiln9 at I2 are the same, in effect, as the burning of sulphur in the wellknown process of producing Vcommercial sulphuric acid. The economicadvantage of this is that the sulphur obtained from this waste productis, at the present day, Worth $18.00 a ton.

In the above described kiln 9, after the period of reduction, the FeOplus metallics material is preferably allowed to cool under gas. Thiscooling of the material under gas preferably takes place in the kiln 9,and therefore constitutes merely another stage of the step shown 'inFigur 2 of the drawings.

Instead of reducing the FezOa to FeO and metallics by reduction undergas in the kiln 9, I cor template in practice using a shaft method ofreduction, as shown diagrammatically in Figure 3, wherein the FezOa iscascaded in a shaft I5 through an ascending current of a reducing gasI6, which may be cracked methane, butane, or ordinary illuminating gas,as an alternative to the reduction under gas stage of the step shown inFigure 2. Such a method of reduction is well known in the art. Theresulting material is, as before, FeO plus 12%" to 20% metallics.

This material, so obtained, is then ground to a ground or powdered formas indicated at I 9 in Figure 4, the grain size or degree of fineness ofthe ground particles varying with variations in the size of briquets Idesire to make. In ordinary practice, for a. briquet of the class to behereinafter described, this material is preferably ground so as to passthrough an 80-mesh United States standard screen.

This finely ground or powdered material I8 is then mixed mechanically bya suitable mixer I9 with a small amount of binder material 20. Thisbinder material may be a mixture of 50% ordinary turpentine rosindissolved with heat in 50% petroleum jelly. The proportions are veryseldom over 5% of binder in a total briquet. In some cases, dependingupon the product which I wish to make, I also incorporate up to as highas 5% of finely divided carbon, such as petroleum lamp black, toproduceCO and a more porous condition in the resulting product. Myreason for using this is to accelerate reduction in firing the briquetsto reduce the oxide to pure (or substantially pure) iron, which step ofreduction will be hereinafter described. By using turpentine rosin Ialso get a nal amount of carbon from the rosin and also from thepetroleum jelly to assist in the reduction.

In making use of binders in forming the material for briquetting, I havementioned but one, that consisting of petroleum jelly and turpentinerosin, but I have used oil, water, glucose and foundry binders of allkinds, and no not wish to be construed as limiting the present inventionto any particular type of binder.

It is oi importance that the FeO containing metallics be thoroughlymixed with the binder used and the lamp black, as they should beperfectly disseminated throughout the mass and of perfect mechanicalmixture. It is desirable, therefore, that the mixing be carried out in amixer of such type as will produce this result. Mixers of the sigmablade type are adaptable for this work.

The perfect mechanical mixture of iron oxide and graphite and/or lampblack (carbon) is then packed into a briquetted shape or articlepreferably by means of the high speed percussive briquetting method ofmy copending application filed December 28, 1933, Serial No. 704,284.

This high speed percussive briquetting method and the means therefor isshown in more or less diagrammatic form in Figure 6. It is to beunderstood that the brquetting means shown in the drawings is notnecessarily the approved means, but merely illustrative of a suitablemeans in elementary form for carrying out the high speed percussivebriquetting action which I employ.

The percussive or vibration briquetting device shown in Figure 6comprises a rigid base 25 having positioned thereon a hardened steelmold 26. The mold 26 is preferably sectionalized radially atcircumferentially spaced locations about the mold cavity 21 denedthereby, and the inner surfaces of the mold sections are preferablyground to form a smooth finished mold cavity defining surface.

The lower ends of the mold sections 26 are provided with integralflanges 28, the lowersurfaces of which are finished and seat upon thefinished upper surface 29 of the base 25. Suitable clamping devices 30cooperate with the flanges 28 to clamp the mold sections firmly in placeupon the base 25, and the external surface 32 of the mold 26 is taperedupwardly from a larger diameter at the ange 28 to a smaller diameter atthe upper end of the mold. A steel ring 33 may be interposed between theclamping devices 88 and the top of the flange 28, and a tapered steelholding ring 85 is slipped into place about the mold sections 28 to holdthe mold sections firmly together and tightly closed about the moldcavity 21. 'I'he inner surface 38 of the continuous ring 35 is taperedfrom a larger diameter at the bottom to a smaller diameter at the top,this taper 36 corresponding to the taper 32 so that as the ring 35 isforced down over the mold sections the tapered surfaces will cooperateto bind and hold the mold sections together by a wedge-like action.

The particular means shown is for producing Yan annular briquette havinga cylindrical external surface, at parallel ends, and a concentricopening such as is adaptable for use as a main bearing or any bearing,or as a valve guide or the like, and for that purpose is provided withan upright steel core 38. It is to be understood,

` however, that the core 38 may be omitted where a solid cylindricalbody ls desired, and that the mold may be formed to produce a widarangeof other shapes as suitable or desired.

The core 38 is disposed concentrically within the mold cavity 21, andmay be positioned accordingly upon the base 25 by engagement of itslower end in a recess 88 in the upper surface of the base. A steel ring48, the external diameter of which ts snugly within the mold cavity 21,is placed over the core 38 and down upon the base 25, and the mixture ofiron oxide, graphite and/or lamp black (carbon) and binder is thenplaced in the mold cavity 21, down upon the ring 40, and around the core38. A second steel ring 42 may be placed over the core 38 and into themold cavity, down upon the top of the mixture, indicated generally at43.

The driving head or ram 45 ts slidingly within the cavity 21 and iscored at 4B to operate slidingly over the upper end of the core 38.'I'his driving head or ram 45 is rapidly vibrated by an air hammer,electric hammer, or other suitable means, indicated more or lessdiagrammatically at 48, and a reaction absorbing block 50, preferably inthe form of an oak wood ring A inch thick is interposed between thesteel ring 42 and the lower end of the driving head 45. This ring orblock 58 may be of any other suitable or preferred material which willabsorb the reactions to the rapid vibrations or percussive actions ofthe driving head 45.

In an illustrative embodiment of the invention,

'the vibration or percussion producing means 48 may be a 21/2 inchpiston Ingersoll-Rand jack or air hammer, although other rapidlyvibrated ramming or percussion devices are contemplated within the scopeof the present invention.

The vibrations or percussions are rapid and, in one method of carryingout the invention, are of the order of about 800 to 1000 vibrations orpercussions per minute. I find that this vibrating or percussive actionproduces rapid percussions in the material, and that this produces abriquet of homogeneous density and enables producing briquets as largeas desired without laminations in or cracking of the structure of thebriquet, and without variations in the structure from end to end, andparticularly along the intermediate portions between the ends. Thispercussive briquetting method further makes it possible to produce thedesired briquet formy of practically any size and of perfect homogeneitywithout excessive pressures and with an extremely low cost machine. Fora briquet 2% inches in diameter in the forming of the briquets.

by 5 inches long with a 15h-inch opening and having a wall %inch inthickness, the material is filled in the mold to a length of about 12inches. and is brought down to the 5-inch length by the vibration orpercussive action above described.

In briquetting, the grain size is rather important. It has been found byvarious sizings that different densities of briquets can be made, so Ido not wish to linut myself to any particular grain size in theformation of these briquets.

The accepted method at the present time of forming briquets from powdershas been to use a hydraulic press, or high pressure mechanical pressessuch as the Colton press. Thesepresses make use of extremely highpressures usingas much as 35,000 to 75,800 pounds per square inch And itis impossible, in forming a briquet in a hydraulic press with acontinuous application of the pressure,

to get a briquet of homogeneous density even wherethe pressure isapplied from both ends of the mold or die. The resulting briquet,particularly if larger than that required for a relatively small bearingor bushing, is not homogeneous from end to end. 'Ihis has beenestablished. By making use, however, of an extremely rapid percussiveaction I am able to make briquets of any size and any length, the onlylimiting factor being the size of the air cylinder or hammer used in theformation of the briquet. The more rapid the percussive action, thebetter the briquet.

'I'he cost of briquetting machines making use of extremely highpressures, either mechanically or hydraulically applied, has beenextremely great. For example, to produce a briquet 2% inches in diameterby 5 inches long with a 11/2- inch opening and having a wall :3A-inch inthickness, it would take a hydraulic press capable of producing a rampressure of not less than 600,000 pounds. Such a press would cost in theneighborhood of $45,000.00. I can produce these briquets with thepercussive action referred to continually and rapidly at a total cost ofequipment which is only a very small percentage oi' the cost abovereferred to.

The briquet 55 so obtained is then dried in a suitable drier 58 (Figure7) at a temperature of from 300 F. up to 400 F., and then is of sumcientstrength to withstand all mechanical handling from this step to the nextstep shown in Figure 8.

The briquet is then placed in a tubular retort 58, such as an 8-inchpipe with ll/z-inch openings 58 and 50, one at each end, to admit areducing gas at 59 and allow the same to pass through the pipe 58 and beignited at the outlet 80. The gas used at this stage of the process maybe any of the reducing gases, such as hydrogen or illuminating gas. Theretort 58 is then fired exteriorly. brought to a temperature of 1800 F..and held at that temperature until all of the FeO in the briquet isreduced to pure or substantially pure metallic iron. This may bedetermined by taking periodical gas samples at the outlet 80 of the tube58 and determining the CO2 content of the gas. It has been found thatwhere an ordinary illuminating gas contains as much as 11/2% CO2 onadmittance to the tube 58, a showing of 1.8% to 2% CO: at the outlet 80is a very close indication that al of the oxide is reduced.

When the oxide has been reduced, the temperature in the pipe 58 israised to about 2100 F. and held there for a period of approximately anhour. This temperature is maintained for this period for the purpose ofsintering, and by the word Lsintering I mean that the metallic particlesbecome soft enough below the melting point of iron to weld or coalesceone into another, producing thereby a porous structure of greatmechanical strength. The briquet has minute communicating poresdistributed throughout the body thereof. The period of sintering and thetime of reduction varies with the size of briquet within the tube 58. Asa typical example, the period of reduction would be approximately 2hours and 20 minutes, and the period of sintering would be 45 minutesfor reducing a briquet 1% inches in diameter with a 1 inch orice in thecenter, to a metallic sleeve such as would be adaptable for a shaftbearing.

I do not intend to be limited to the retort type of reduction, butcontemplate using a contin uous moving hearth, either electrically orgas fired furnace. Similar furnaces 'are now in use for the welding ofsteel parts to copper in hydrogen or atmosphere.

The gas and temperature control during the period of reduction of thebriquets is very .important. 'I'he type of gas used is of greatimportance as it is not desirable to use gas which cracks at high heat,thereby liberating excessive carbonaceous matter, as the same wouldcontaminate the reduced iron and produce an unsatisfactory product. I donot wish, however, to limit myself to the exact temperatures or exactgases herein disclosed, as further experimentation may show that thesame results may be obtained at a different temperature range, or withdifferent gases.

By previously cracking butane before admitting it to the reductionretort it is possible to obtain a very-cheap and efficient gas for thepurpose of reducing the iron oxide. During the process of reduction thecarbonaceous material within the briquet is broken down by heat, and CO,or carbon monoxide, is liberated. 'Ihis gas is an extremely goodreducing agent and assists materially in the reduction in the briquets,so that I really have two gases aiding the process of reduction, thesebeing hydrogen and carbon monoxide. During the process of reduction,water is formed, and it is possible, by condensing this water, to use itas an indicator as to what stage the reduction has reached. This,together with the CO2 determination, gives rather accurate control ofthe reduction.v

After firing in the tube or retort 58, the briquet 55 is cooled undergas. In making use of the tube or retort 58, as soon as the period ofreduction ofthe oxide of iron is over, the valve at the outlet end ofthe tube is closed and no further gas is used or consumed during theperiod of sintering or cooling.

The retort may be made of high temperature metals, such as chrome iron,or it can be manufactured very similar to the saggars now in use in manyindustries, or of refractory clays, carborundum, magnesite, or alundum.

A briquet produced in this manner can be controlled in size so aspractically to need no machining to produce a finished article. Owing tothe ductility of the metal so produced, it is perfectly feasible to givethe final finish by a stamping operation, thereby eliminating allmachining, although, of course, the article may be machined to size ifdesired.

The briquetting of the metal by rapid vibrations to produce percussiveaction causes the metal to fill and pack the mold even in intricateshapes, the material apparently flowing by the rapid vibrations orpercussions caused by the rapping of the air hammer or the like.Intricate shapes may be formed.Y 'I'he nnal density depends upon theamount of rapping and the proportion of iron and graphite or othercarbon in the mixture.

The briquetted and reduced mass, i. e., the porous iron mass ischaracterized by lightness, uniformity of porosity and ofdenslty and bya spongy structure. In metal made according to the prior process ofsintering grains of metal, where powdered metal` is sintered, thestructure consists of grains adhering or bonded to each other. Hence,fracture tends to occur across the joints or sintered bonds.

According to the present process, the resultant mass or end product is aunitary homogeneous mass which somewhat resembles a sea sponge instructure. The pores are of minute capillary size, and the walls whichare all integral, being formed in situ, appear to be webs or lms mergedinto each other. The pores intercommunicate freely. The difference instructure is therefore pronounced,.and the difference in fracture showsthe difference in structure. No loose grains are released by wear,cutting, or fracture, as is the case with sintered metal powder. Neitherdoes the material of my invention tend to disintegrate into powder orparticles upon being subjected to mechanical stresses.

Where the metal is to be used for bearings, pistons, or other structureshaving frictional surfaces it is desirable to impregnate it with alubricant, preferably oil. The preferred method of doing this is under avacuum, in hot oil, or in oil at a temperature of approximately 240 F.,thereby insuring that there is no moisture present. In about twentyminutes, under a vacuum of 28 inches, the metal is thoroughlyimpregnated with any lubricating oil. This oil permeates through theintercommunicating pores of the structure and the metal so impregnatedsweats or exudes oil when heated, and takes it in or absorbs it oncooling. The result of this is that where the metal is used in abearing, bushing, valve guide, piston, or other part having a frictionalsurface, movable upon the surface of another part or upon which thesurface of another part is movable, the lubrication of the cooperatingsurfaces is assured with the initial movement between such surfaces andwithout waiting, as in an internal combustion or Diesel engine, for asupply of oil to be sent up thereto.

By varying the density of the briquet and also by varying the amount offinely divided carbon which I incorporate in the briquet, I am able toproduce a structure of varying degrees of porosity, running Afrom as lowas 10% porosity to as high as porosity. During the process of reductionthe percentage of metallics in the briquet increases the heatconductivity of the briquet and accelerates the reduction, therebycutting down the period of time and producing a more coherent andmechanically stronger porous mass.

It is possible by the incorporation of other oxides in an admixture ofFeO (iron oxide) to produce alloys of a porous structure such as amixture of iron oxide and copper oxide, or a mixture of iron oxide andmanganese oxide. It has even been found possible to make use of thehighly difcult chromium oxide with iron oxide to produce porous alloyslike the above.

The gas during the reduction period should be controlled so that largequantities of carbon are 75 not produced in the case of usingilluminating gas for reduction, 'but it is contemplated in actualmanufacture to make use of gas that has been cracked and contains verylittle carbonaceous material, as already described.

I have made use of FezOa in the formation of briquets and have reducedthe same and produced a porous structure similar to that produced by thereduction of FeO, but the length of time necessary for reduction is somuch greater than reducing FeO that from an economic standpoint FeOcontaining metallic iron is a much less costly method. However, I do notwish to limit myself to the production of this material from FeO alone,but wish to cover all forms of iron oxide. be they Fe203, Fes04, or FeO,for the production of this type of material.

By making use of copperas or ferrous sulphate I produce a purer, moreductile iron than can be commercially produced in any other way. 'I'hepossibilities of this iron are not limited to the articles hereinrecited, nor to articles impregnated with oil and having frictionalsurfaces, or even to the formation of porous structures.

In making use of this material as a bearing, bushing, valve guide,piston, or the like, its low coeilicient of expansion is an importantaspect. This low coeiicient of expansion with the lubri- Acationproduced where the metal is impregnated with Oil, renders impossible theseizing or scoring of a shaft, even at extremely high temperatures. Themetal itself, even when dried, has a low coefficient of friction. In thecase of bearings or bushings, they are adapted not only for heavy loadsat slow speeds but also at high speeds. The cost of the metal is low,and its weight is low, similar to aluminum, making it especially adaptable for pistons for internal combustion engines, Diesel engines, steamengines and other engines, and the light weight is obtained without ahigh coeiiicient of expansion, as is the case of aluminum pistons. Ialso contemplate the use of the metal for aeroplane parts and to replacealuminum wherever it is possible that weight and cost are a factor.

'Ihe ductility of this metal is shown as follows:

A "/8 inch round briquette 11/2 inches long, under a compressive load of43,000 pounds per square inch, was reduced in length from 11A inches to3A of an inch, showing no sign of rupture, and simply became a denser,more coherent mass.

Tensile strengths vary with the porosity. The tensile strength of thematerial may be increased by the addition of 5% copper to the briquet,and probably greater tensile strengths can be obtained by making use ofother alloys.

In oiling, I frequently make use of an oil containing varyingpercentages of colloidal graphite which prepares and gives a quickbearing surface.

In making u'se of mill scale to produce a porous iron structure, thegeneral run of mill scale has mechanically included in it a certainamount of siliceous material which contaminates. This may be removedfrom the mill scale by any of the well known gravity processes, such astabling over a Wilfley table, or might, in some instances, be removed bymagnetic concentration.

Mill scale consists essentially of Fe304, FeO, and a'small percentage ofmetallic iron. It is more or less diicult to reduce in that form, owingto its glaze or impervious nature; so, in making use of mill scale,after I remove the siliceous or foreign material from the oxide, Ipartially reduce the mill scale by making use of the same type of rotarykiln as I spoke of formerly in reducing FeiOa obtained from copperas.Only, in the case of mill scale, it is not necessary to calcine, as itcontains no sulphur. I partially reduce the mill scale by making use ofilluminating gas at a temperature of approximately 1700 F., therebyobtaining a product which is principally FeO and metallic iron. Thisproduct. when ground, can be briquetted and red to reduce the cxide topure (or substantially pure) iron and of an open porous structure, insubstantially the manner set out in connection with the FeO obtainedfrom copperas,

An article formed in accordance with the present invention may be oiledfrom one side, for example, a side whichY is exposed, and the oil willseep or permeate through the intercommunicating pores to the other side,or sides, which may be concealed.

Where an article formed of the present material is impregnated with oilthe oil will, upon heating of the article, expand so much faster thanthe metallic material that the article will sweat or exude oil whenheated and take in or absorb the oil when cold.

I could grind and briquet the mill' scale without any previoustreatment, but the time of reduction in a briquet form would be greaterand more costly. However, mill scale as a source of raw material is oneof the sources of raw material that the appended claims are intended tocover.

I claim:

1. The method of forming a substantially pure iron of open porousstructure which comprises dividing an oxide of iron into relatively fineparticles, adding a slight amount of carbon, mixing with a binder,packing the mixture into a briquetted shape by a series of percussiveblows, and firing the shape in the presence of a reducing agent toreduce the oxide.

2. A process which comprises removing the siliceous or foreign materialfrom mill scale, reducing the mill scale with the siliceous or foreignmaterial removed to a product which is principally FeO and metalliciron, dividing the FeO and metallic iron into relatively line grains,mixing the same with a binder, packing the mixture into a briquettedmass by a series of percussive blows, and treating the mass to reducethe oxide of iron to substantially pure iron of an open porousstructure.

3. The method of forming an integral body of substantially pure iron ofintercommunicating porosity which comprises dividing FeO and metallicsinto relatively iine particles, packing the particles into a briquettedshape by a series of percussive blows and firing the same in thepresence of a reducing agent to reduce the oxide into a porous integralbody.

4. An integral ferrous body of porous structure, comprising a ductilemass of iron of spongy character produced by reducing to metallic formin situ a mass of iron oxide compacted by a series of percussive blows.

5. As a new material, an integral ductile spongy mass of iron havingintercommunicating pores of minute size, the iron of the mass beingformed in situ by reduction of an oxide compacted by a series ofpercussive blows, said mass having no tendency to disintegrate intopowder under mechanical stress.

6. The process of forming an integral body of porous iron whichcomprises dividing iron oxide into relatively ne particles, mixing thesame with nely divided carbon, packing the mixture into'a briquettedshape by a series of percussive blows, and firing the shape in thepresence of a. reducing agent to reduce the oxide in situ into anintegral substantially homogeneous mass of porous ductile iron.

7. The process of producing an integral ductile spongy mass of ironhaving intercommunicating pores of capillary size, which comprisesmixing powdered iron oxide and a small amount of a heavy binderrelatively high in carbon and of high viscosity to produce a mass whichwhen compacted will hold its shape, disposing the mass in a mould,ramming the mass into the mould with high frequency percussive blows tocause compacting of the mass, then firing the mas in a reducingatmosphere to reduce the iron oxide in situ to metallic iron.

8. 'I'he method of forming an integral body of substantially pure ironof controlled porosity, which comprises mixing iron oxide and metallicsboth in relatively ne particles with powdered carbon, compacting thesame into a definite a definite shape, removing the shape from themould, and ring the shape in the presence of a reducing agent to producein situ an integral mass of spongy iron.

10. The method of forming an integral bodyof substantially pure iron ofintercommunicating porosity which comprises dividing an oxide of ironand metallics into relativelyV fine particles. packing the particlesinto a briquetted shape by a series of percussive blows, and firing thesame in the presence of a reducing agent to reduce the oxide into aporous integral body.

1l. The method of forming an integral body of metal to produce amaterial having a bearing surface of relatively long life whichcomprises mixing relatively fine particles of iron oxide and carbon,subjecting the mix to a series of percussive blows to form a briquette,and firing the briquette at a temperature oi about 1700" F. in thepresence of a reducing agent until it is reduced to substantially pureiron.

12. The method of forming an integral body of metal to produce amaterial having a bearing surface of relatively long life whichcomprises mixing relatively fine particles of iron oxide and carbon,subjecting the mix to a series of percussive blows to form a briquette,ring the briquette at a temperature of about 1700 F. in

`the presence of a reducing agent until it is reduced to substantiallypure iron, and sintering the briquette at a temperature of about 2100 F.to produce a relatively porous structure having relatively greatstrength.

13. The method of forming an integral body of metal to produce amaterial having a'bearing surface of relatively long life whichcomprises mixing relatively fine particles of iron oxide and carbon,subjecting the mix to a series of percussive blows to form a briquette,firing the briquette at a temperature of about 1700 F. in the presenceof a reducing agent until it is reduced to substantially pure iron,sintering the briquette at a temperature of about 2100 F. to produce arelatively porous structure having relatively great strength, andimpregnating the sintered briquette with a lubricating medium to renderit self lubrieating.

CHARLES FREDERIC SHERWOOD.

